1. Field of Invention
The present invention relates to a method for treating etching solution. More particularly, the present invention relates to a method for purifying fluoride etching solution.
2. Description of Related Art
As to waste etching solutions discarded from the substrate etching processes of the semiconductor, liquid crystal display (LCD) and solar energy industries, they usually include unspent etching solutions (strong acids or alkalines such as hydrogen fluoride) and impurites (anions, cations and metal oxides) etched from the devices of the semiconductor, LCD and solar energy. Such discarded solutions increase environmental burdens and lower economical benefit.
As exemplified by the fluoride etching solution, it is widely used in wet processes of the silicon wafers, glass substrates, silicon substrates of solar batteries and so on. The source of the fluoride etching solution includes unspent etching solutions and waste etching solutions used in many times of wet etching processes. After being used many times of wet etching processes, the waste etching solutions contain various impurities such as anions, cations and metal oxides) etched from those substrates. More impurities accumulated in the etching solution exhibit the lower etching rate of the etching solution and adversely affect the production performance and the etching quality. When the impurities accumulated in the etching solution severely affect the etching quality, such etching solution in the whole tank must be replaced with a fresh etching solution.
However, the discarded waste etching solutions increase environmental burdens and lower economical benefit. Besides, the conventional methods for purifying waste etching solution have been proposed, but their processes are too complicated, expensive and inappropriate to reuse the waste etching solution. Furthermore, the waste etching solution is hardly processed to the fluoride etching solution that meets the requirement of the industrial processes.
As described above, it is necessary to provide a method for purifying fluoride etching solution for overcoming the problems of reuse of the waste fluoride etching solution.